In general, a fuel cell as disclosed in Japanese Patent Laid-Open No. 2013-065497 is known. The fuel cell described in Japanese Patent Laid-Open No. 2013-065497 is provided with a single battery cell and a pair of interconnectors provided on the fuel electrode side and the air electrode side of the single battery cell, respectively. Between the pair of interconnectors, a cell holder, an insulating portion, and a gas seal separator are provided to surround the single battery cell. The gas seal separator is provided to lie across the insulating portion and the single battery cell, and shuts off the fuel electrode side and the air electrode side of the single battery cell.
When the gas seal separator is made of a metal foil having a relatively small thickness, there is such a disadvantage that the gas seal separator deforms to be corrugated. Thus, in the fuel cell described in Japanese Patent Laid-Open No. 2013-065497, corrugated deformation is suppressed by coating both surfaces of the gas seal separator with titanium oxide.